Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F110/04—Monomers containing three or four carbon atoms
  • C08F110/06—Propene
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]

Definitions

• the invention relates to a process for synthesis of a Ziegler Natta procatalyst, used in the polymerization of alpha olefins, involving multistage treatment of magnesium alkoxide with used as well as recovered mixture of titanium tetrachloride and chlorobenzene (mixed solvent) and successive washing of the product with used as well as recovered hexane.
• the invention also relates to the procatalyst synthesized by the process and to the polymerization process using the procatalyst.
• Ziegler Natta type catalysts used for polymerization of alpha-olefin usually involve a procatalyst comprising titanium, magnesium, chlorine, an internal donor and a cocatalyst which is essentially an organo aluminium compound.
• the performance of such catalysts is further complemented by the usage of an external electron donor.
• the procatalysts are usually synthesised by contacting magnesium alkoxide with a mixed solvent (a mixture of TiCl 4 and chlorobenzene) in the presence of an internal donor, in multiple stages, adding fresh TiCl 4 during each stage.
• a compound of the formula TiCl 3 OR (where R is an alkyl or aryl group) is formed along with solid product.
• TiCl 3 OR remain dissolved in the mixed solvent as a contaminant.
• Such contaminated solvents raise waste disposal issues and therefore the contaminant need to be eliminated.
• the contaminants in the solvents are most commonly removed by distillation process. The process of distillation is, however, energy intensive, require elaborate equipments and the distillation by itself generate hazardous wastes.
• US 4683215 describes a process for synthesis of Ziegler Natta procatalyst in which the TiCl 3 OR contaminant in used mixed solvent is removed by treatment with benzoyl chloride which converts TiCl 3 OR to a solid addition complex. Further, the complex is separated off from the liquid phase and the liquid phase, after removal of the complex is added with fresh TiCl 4 and is used to treat the solid mixture containing magnesium ethoxide and the procatalyst product.
• purification of effluent after each stage in a multistage reaction of magnesium alkoxide with mixed solvent, is rather cumbersome and fresh solvents used each time after purification would build up solvent inventory.
• TiCl 3 OR contaminant accumulates after each purification step and the accumulated contaminant would raise waste disposal issues.
• the process for synthesis of Ziegler Natta procatalyst involves maximum utilization of mixed solvent by its multistage treatment with magnesium alkoxide.
• the process of the invention also involves recycling the internal donor and successive washing of the product with used as well as recovered hexane ⁇
• An object the invention is to provide a non hazardous , low waste generating , efficient and economical process for synthesis of Ziegler Natta procatalyst.
• Another object of the invention is to provide an efficient method of purifying the procatalyst by successively washing the procatalyst with used as well as recovered hexane.
• Another object of the invention is to provide an active catalyst, for Ziegler Natta polymerisation of olefins, devoid of unreacted magnesium alkoxide.
• a further object of the invention is to provide a process for Ziegler Natta polymerization of propylene resulting in polypropylene with high productivity.
• the invention provides a process for synthesis of Ziegler Natta procatalyst involving multiple stage treatment of magnesium alkoxide with used as well as recovered mixed solvent.
• the invention provides a process for the synthesis of a Ziegler Natta procatalyst, the process comprising first treating magnesium alkoxide with a twice used mixed solvent of TiCl 4 and chloro benzene to form a first stage product, then treating the first stage product with a once used mixed solvent of TiCl 4 and chlorobenzene to form a second stage product and finally treating the second stage product with mixed solvent recovered by treatment of effluent from the first treatment with benzoyl chloride so as to convert contaminant of formula TiCl 3 OR in the effluent to an addition complex which is precipitated, filtered off and hydrolysed to recover ethyl benzoate and to form Ti(OH) 4 as a side product, the product after final treatment being subjected to a plurality of successive washing steps with used as well as recovered hexane.
• the invention provides a process for the synthesis of a Ziegler Natta procatalyst, the process comprising first treating magnesium alkoxide with a twice used mixed solvent of TiCl 4 and chloro benzene to form a first stage product, then treating the first stage product with a once used mixed solvent of TiCl 4 and chlorobenzene to form a second stage product and finally treating the second stage product with mixed solvent recovered by treatment of effluent from the first treatment with benzoyl chloride so as to convert contaminant of formula TiCl 3 OR in the effluent to an addition complex which is precipitated, filtered off and hydrolysed to recover ethyl benzoate and to form Ti(OH) 4 as a side product, the product after final treatment being subjected to a plurality of successive washing steps with used as well as recovered hexane wherein the treatment with the mixed solvent is carried out at a temperature in the range of 90- 110 0 C, preferably in the range of 95 to 98 0
• the invention provides a process for the synthesis of a Ziegler Natta procatalyst, the process comprising first treating magnesium alkoxide with a twice used mixed solvent of TiCl 4 and chloro benzene to form a first stage product, then treating the first stage product with a once used mixed solvent of TiCl 4 and chlorobenzene to form a second stage product and finally treating the second stage product with mixed solvent recovered by treatment of effluent from the first treatment with benzoyl chloride so as to convert contaminant of formula TiCl 3 OR in the effluent to an addition complex which is precipitated, filtered off and hydrolysed to recover ethyl benzoate and to form Ti(OH) 4 as a side product, the product after final treatment being subjected to a plurality of successive washing steps with used as well as recovered hexane wherein molar ratio of benzoyl chloride to TiCl 3 OR in the effluent during the treatment with benzoyl chloride is in the
• the invention provides a process for preparation of a Ziegler Natta procatalyst wherein the procatalyst is subjected to a first washing step using thrice used hexane, a second washing step using twice used hexane and a final washing step using hexane recovered from the effluent of the first washing step.
• the invention provides a Ziegler Natta procatalyst prepared by first treating magnesium alkoxide with a twice used mixed solvent of TiCl 4 and chloro benzene to form a first stage product, then treating the first stage product with a once used mixed solvent of TiCl 4 and chlorobenzene to form a second stage product and finally treating the second stage product with mixed solvent recovered by treatment of effluent from the first treatment with benzoyl chloride so as to convert contaminant of formula TiCl 3 OR in the effluent to an addition complex which is precipitated, filtered off and hydrolysed to recover ethyl benzoate and to form Ti(OH) 4 as a side product, the product after final treatment being subjected to a plurality of successive washing steps using hexane .
• the invention provides a process of polymerization of propylene, the process comprising contacting propylene with a catalyst system comprising a procatalyst, an organoaluminium co-catalyst and 4- ethoxyalkylbenzoate as the electron donor, wherein the procatalyst is prepared according to the process of the invention.
• the invention provides an economical and low waste generating route for the synthesis of procatalyst for propylene polymerisation.
• the synthesis is suitable for preparing both alkyl benzoate (monoester) based as well as dialkyl phthalate (diester) based catalyst systems.
• the synthesis is carried out in multiple stages in order to achieve maximum conversion of the reactants.
• the procatalyst is purified by successive washings utilising used as well as recovered hexane. This ensures that the solid procatalyst after the final stage treatment has maximum purity and is devoid of magnesium alkoxide in the unreacted form.
• the process of the invention results in a procatalyst of good activity, apart from efficiently utilizing the reaction solvents and washing solvent.
• the magnesium alkoxide reactant used for the synthesis of the procatalyst is obtained by a controlled reaction of magnesium with a mixture of alcohols. Further, the magnesium alkoxide used is a shape controlled magnesium alkoxide.
• magnesium alkoxide is treated with twice used and once used mixed solvent of titanium tetrachloride and chlorobenzene as well as mixed solvent recovered through benzoyl chloride treatment of impure mixed solvent (mixture of titanium tetrachloride, chlorobenzene and titaniumchloroalkoxy impurity) generated from the reaction.
• impure mixed solvent mixture of titanium tetrachloride, chlorobenzene and titaniumchloroalkoxy impurity
• Titaniumchloroalkoxy (TiCl 3 OR) impurity is removed in the form of a TiCl 4 .alkyl benzoate addition complex, which is removed from liquid phase by filtration.
• the solid addition complex generated from benzoyl chloride treatment is then hydrolyzed to obtain ethylbenzoate (internal donor) and titanium hydroxide.
• the recovered ethylbenzoate is reused for the reaction, while titanium hydroxide is obtained as a vital non-hazardous side product.
• Titanium hydroxide is a valuable raw material for producing titanium dioxide.
• the procatalyst synthesized by the process of the invention is used for the polymerization of propylene.
• the polymerisation is carried in the slurry phase, gas phase as well as in the bulk phase.
• the selectivity control agents used for. the polymerization include, but are not limited to Ethyl-4-ethoxy benzoate, Ethyl-4-propoxy benzoate, Ethyl-4-isoprpoxy benzoate, Ethyl-4- Isobutoxy benzoate, Propyl-4-ethoxybenzoate, Isopropyl-4-ethoxybenzoate, Butyl-4- ethoxybenzoate and Isobutyl-4-ethoxybenzoate.
• magnesium alkoxide (2-3 wt % methoxy and 70-74 wt% ethoxy derivative of magnesium) was reacted with 272 ml of titanium tetrachroride and chrolobenzene mixture (1 :1 v/v) along with 4.4 ml of ethylbenzoate at 96-98 0 C for 60 minutes.
• the first stage treatment twice used mixed solvent obtained after the second stage treatment was treated with magnesium ethoxide.
• the first stage treatment resulted in a conversion of about 94 to 96%.
• the solid obtained after the first stage treatment was filtered off the mixed solvent.
• the mixed solvent (thrice used mixed solvent) obtained was subjected to benzoyl chloride treatment and the mixed solvent is recovered after the treatment.
• the solid product of the first stage treatment was further treated in a second stage with once used mixture of titanium tetrachloride and chlorobenzene (recovered after third stage treatement) at 96-98 0 C for 30 minutes.
• the second stage treatment resulted in a conversion of around 97 to 98 %.
• the solid product after the second stage treatment is filtered off the mixed solvent and further treated in a third stage with recovered mixture of mixed solvent (obtained after benzoyl chloride treatment) for 96-98 0 C for 30 minutes.
• the third stage treatment resulted in a conversion of greater than 99.5%.
• Solid product after the third stage treatment is filtered off the mixed solvent and washed successively with thrice used/ twice used and once used hexane and finally with recovered hexane for removal of excess titanium chloride and other impurities.
• the procatalyst contain 2.8-3.4 wt % titanium, 14-16 wt % ethyl benzoate and has a ethoxy content of 0.1-0.3 wt %.
• the solid procatalyst so obtained was used for polymerization of propylene.
• Example -2 Benzoyl chloride treatment of effluent
• the titaniumtetrachloride-ethylbenzoate adduct was hydrolyzed with water. Three washes of water was given to collect the organic phase. Later, organic phase was distilled to get pure ethylbenzoate which was recycled for reuse. The aqueous liquid which was acidic in nature was neutralized with caustic soda to give a white precipitate which is hydroxide of titanium that was removed by filtration.
• Table 1 Comparison of slurry phase polymerization productivity using procatalyst prepared by the procedure in example 1 with procatalyst prepared by treatment of magnesium alkoxide with fresh solvent during each stage of multi stage treatment.
• the process of the invention makes efficient use of the mixed solvent used for preparation of the procatalyst apart from avoiding the steps of purification of the mixed solvent each time it is used.
• the invention therefore, provides enhanced process efficiency in the catalyst preparation process leading to savings in cost and effort.
• the process of the invention prevents build up of solvent inventory during scaling up of the synthesis.
• the process of the invention avoids issues related to hazardous waste disposal and at the same time recovers a valuable reagent for the reaction.

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• 2008
  • 2008-08-25 WO PCT/IN2008/000533 patent/WO2009116057A2/en active Application Filing
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